There are many situations in which a portable heater is extremely useful. For instance for outdoor sporting events, such as football games, in cold weather season areas, a portable heater can make the difference between comfort and discomfort and being able to stay until the end of the game or having to leave early. Military personnel in cold weather areas would have their comfort greatly enhanced with a portable heater, especially one capable of heating up food, coffee, etc., on an individual basis. An effective portable heater could greatly enhance comfort, and perhaps even save lives, in emergency situations such as snow storms, power failures, and the like, and for all people involved in outdoor wintertime work or recreational activities.
In order to be effective, a portable heater must be able to generate significant amounts of heat over a relatively long period of time (e.g., 8 to 10 hours), must not be dependent upon stationary, preexisting energy sources, must be safe, and must be able to generate heat without generating significant amounts of pollution.
According to the present invention, a portable heater is provided that is capable of achieving all of the above-enumerated requirements. The portable heater according to the present invention is light in weight, convenient to carry, and provides a safe, comfortable heat source for one or more persons for 8 to 10 hours utilizing a single container of fuel. The heater according to the present invention is capable of burning butane (which may be provided in replaceable liquefied butane canisters) instead of propane for increased safety, weight reduction and ease of canister replacement. Heat is provided without flame for enhanced safety, and there is minimal production of pollutants (e.g., hydrocarbons about 10 ppm or less, carbon monoxides about 1-2 ppm, and nitrogen oxides about 0.1 ppm).
The portable heater according to the present invention includes as one of the important component parts thereof a combustion chamber assembly. The combustion chamber assembly includes an elongated tubular combustion chamber of heat-resistant metal having a first exhaust end, and a second entry end. A second tubular member is mounted interiorly and substantially concentric with the tubular combustion chamber and adjacent the second end thereof. A plurality of screens of heat-resistant metal such as Kanthal are mounted within the combustion chamber in planes substantially perpendicular to the direction of elongation of the combustion chamber, and spaced from the interiormost end of the second tubular member. The second tubular member has a detachable combustible gas feeding portion which extends outwardly past the termination of the combustion chamber second end, and has a plurality of openings formed in the walls thereof for the entry of surrounding air to mix with combustible gas flowing through the second tubular member. A stainless steel honeycomb structure or the like is provided surrounding a portion of the second tubular member within the combustion chamber adjacent the second end of the combustion chamber, the honeycomb structure allowing for the passage of air through the combustion chamber second end around the second tubular member to the screens. The honeycomb structure terminates within the combustion chamber so that an apron is provided by a portion of the tubular combustion chamber past the termination of the honeycomb structure increasing the "chimney action" of the combustion chamber and ensuring that all hydrocarbons pass upwardly and are not bypassed around the heated screens.
The portable heater according to the present invention includes means for receiving a source of combustible gas, a combustion chamber (preferably as described above), and means for providing the transport of combustible gas from the source to the combustion chamber and for the transport of ambient air into the combustion chamber to mix with combustible gas to effect combustion. The screens facilitate combustion without flame (except during initial start-up), and the top of the combustion chamber provides an exhaust conduit to the ambient air for exhausting the products of combustion. A third tubular member having perforations at the second end thereof is provided concentric with the combustion chamber, and is coated over most of the length thereof with a baked-on ceramic. This arrangement provides easy inflow of air and promotes a strong updraft as air rises past the combustion chamber.
A removable piezoelectric element or like ignition means is preferably provided in operative association with the top of the combustion chamber. After ignition, the igniter is removed to allow exhaust of the product of combustion. Ignition can thus be accomplished in a safe, reliable manner without requiring amy extraneous ignition source (such as matches).
The means for receiving a source of combustible gas comprises a hollow bottom casing component including a control valve means mounted therein for receiving a canister of liquefied butane or the like. The control valve provides for reliable, readily controllable metering of combustible gas from the canister to the combustion chamber by a simple relative rotation between upper and lower casing components. The valve includes a neoprene disc having a small diameter hole formed therein. An actuator is moved into and out of compressive engagement with the disc to compress the disc and close off the central opening preventing gas flow, or allow passage of gas through the central opening, respectively. A neoprene washer and metal washer act between the reciprocal hollow tube actuator and the disc.
It is the primary object of the present invention to provide a simple, safe portable heater capable of generating significant amounts of heat over relatively long time periods without requiring a stationary power source, and without significant pollution. This and other objects of the invention will become apparent from an inspection of the detailed description of the invention, and from the appended claims.